Field of the Invention
The present invention relates to a secondary battery.
Description of Related Art
Non-aqueous electrolyte secondary batteries typified by lithium-ion secondary batteries are used in hybrid electric vehicles, electric vehicles, and large-scale electricity storage systems, and the like.
In such secondary batteries, an electrode assembly including a positive electrode plate and a negative electrode plate is housed together with electrolyte in an outer body made of metal and having a mouth, and the mouth of the outer body is sealed by a sealing plate made of metal. In order to prevent the outer body made of metal from directly touching the electrode assembly, the electrode assembly is housed in the outer body while being covered by an electrically insulating sheet.
For example, Japanese Published Unexamined Patent Application No. 2009-170137 (Patent Document 1) and Japanese Published Unexamined Patent Application No. 2009-048966 (Patent Document 2) disclose covering a flattened electrode assembly to be housed in an outer can with an insulating sheet shaped into a box-like or bag-like shape.
Usually, an insulating sheet covering an electrode assembly is flat and is shaped into a box-like or bag-like shape when used. Therefore, a process for shaping a flat insulating sheet into a box-like or bag-like shape is required. In such a process, unshaped flat insulating sheets are stacked, and, from this stack of insulating sheets, insulating sheets are fed one at a time into a shaping jig and shaped into a predetermined shape.
The inventor found that the foregoing shaping process has the following problem. In the stack of insulating sheets, static electricity tends to be generated, and static electricity tends to cause the insulating sheets to adhere to each other. When the insulating sheets are adhered to each other owing to static electricity, a multiple feed may occur when feeding the insulating sheets into the shaping jig. If a multiple feed occurs, this causes trouble and leads to low productivity.